1. Field of the Invention
The present invention generally relates to cellular communication networks, and more specifically to a handoff method for code division multiple access (CDMA) cellular communication networks when a mobile station is communicating with a first base station using a frequency which is different from the frequency of a second base station.
2. Description of the Related Art
Japanese Laid-Open Patent Specification Hei-8-149551 discloses a handoff technique for a CDMA cellular communication system which addresses a problem associated with a mobile station making a handoff attempt from a first base station to a second base station whose frequency is different from the frequency of the first base station. However, this prior art requires a high volume of control data to be exchanged between the base stations and a control station. If handoffs occur frequently, high-speed transmission media would be required between the base stations and the control station to prevent the control traffic from adversely affecting normal communication traffic. In addition, during handoffs the mobile stations are required to transmit preamble sequences as a test signal with such a strength that surrounding base stations can receive and determine their field strengths. The transmission of such test signals would dissipate the battery of a mobile station and shorten the usable lifetime of the battery.